Jul 2 2019
Apologies @Aklapper, the reported issue relates to Parsoid. I think I posted this in the wrong place.
Jun 23 2019
This seems to be broken again, as per https://phabricator.wikimedia.org/T209277 .
Jun 18 2019
This issue is affecting Kiwix clients that need access to the alt text of the fallback images, so that we can typeset equations using MathJax. I'm sure it should be a relatively simple fix. The alt text is provided on equivalent Wikipedia pages.